Static frequency multiplier



July 9, 1968 T. R. KENNEDY STATIC FREQUENCY MULTIPLIER 2 Sheets-Shea 1Filed Jan. 28, 1965 /N VEN TOR THEODORE R. KENNEDY ATTORNEYS y 1958 T.R. KENNEDY 3,392,320

STATIC FREQUENCY MULTIPLIER Filed Jan. 28, 1965 2 Sheets-Sheet 2 I0; I Iil I l 62 0 INVENTOI? THEODORE R. KENNEDY 52 N W fa a a rromvzrs UnitedStates Patent 3,392,320 STATIC FREQUENCY MULTIPLIER Theodore R. Kennedy,Willingboro, N.J., assignor to Inductotherm Corporation, Rancocas, NJ.Filed Jan. 28, 1965, Ser. No. 428,703 22 Claims. (Cl. 321-7) ABSTRACT OFTHE DISCLOSURE A static frequency multiplier for developing a 540 cyclesingle phase output from a three-phase 60 cycle input. The frequencymultiplier includes a phase multiplying transformer with at least sixcoils electrically connected end to end and magnetically coupled inpairs of high and low turn coils, and nine tapping points provided onsaid coils at equally spaced electrical angles. Said tapping pointsbeing connected to non-linear saturable devices connected in sets ofthree with neutral points for developing a three-phase output at threetimes the source frequency, and a frequency tripler connected to theneutral points for providing a 540 cycle, single phase alternatingcurrent to a load.

This invention relates to a static frequency multiplier. Moreparticularly, this invention relates to a static frequency multiplierfor increasing the nominal 60 cycle input frequency to a nominalfrequency of 540 cycles per second.

Frequencies above the nominal commercial frequencies of 50-60 cycleshave been finding increased use. For example higher frequencies havebeen used in fluorescent lighting, high speed motors, induction heating,etc. Static frequency multipliers, used as frequency doublers ortriplers, have been finding increasing favor as economical and efiicientpower sources for devices such as those listed above. For the most partfrequency doublers and triplers rely upon the relatively abrupt magneticsaturation of transformer steel. An harmonic analysis of the saturationeffects indicates that the third harmonic component predominates. Thisthird harmonic, when combined with a three phase power source, providesa convenient and efficient means of converting an input frequency tothree times the input frequency.

For frequencies abovet he third multiple, doubler systems have been usedin one or more cascaded levels, the first level giving a multiple of6(f) where (f) represents the input frequency, the second level being12(f), etc. The present invention is concerned with another approach.That is, the present invention is based upon a method and apparatuswherein a high order phase number is derived from a polyphase primarypower source by a transposer and the phase number thus derived isapplied to a frequency multiplier. As used throughout the specificationand claims, the word transposer refers to a phase multiplyingtransformer described herein; that is, a transformer for raising thephase number of the primary source. The frequency multiplier may be afrequency tripler or cascaded frequency triplers. The frequencymultiplier number is chosen to be equal to the phase number.

Because of the aforesaid high energy third harmonic component duringalternating current magnetic saturation, phase numbers as powers of thenumber 3 have been found to work out to the best advantage. Thus, thesecond power of 3 used as a frequency multiplier of 9 will provide anoutput current at 540 cycles for a 60 cycle three phase source. Ratherthan provide a nine phase integral unit to perform the multiplyingfunction, it has been found advantageous to provide an intermediatestage using three tripling units to provide a three phase system ofthree times the source frequency. This three phase output is thenapplied to a fourth tripler to produce a single phase output of 9 timesthe source frequency. The first stage tripler units utilize threeindividually wound cores, per tripler unit, each wound core excited 120electrical degrees from the other two. The phases of the second andthird tripler units are shifted 40 and electrical degrees respectivelyfrom the first unit thus using up the nine terminals of a nine phaseprimary supply. Each tripler unit of the first stage has its own neutralderived from a Y connection, which neutral points may be used as asource of three phase triple frequency current.

It is a general object of this invention to provide a novel staticfrequency multiplier.

It is another object of the present invention to provide a novel staticfrequency multiplier combining a transposer for developing a high orderphase number and a frequency multiplier.

It is yet another object of the present invention to provide a staticfrequency multiplier having a novel transposer therein.

It is still another object of the present invention to provide a noveltransposer for developing a high order phase number.

It is a further object of this invention to provide a novel transposerfor developing a high order phase number with plural frequencymultipliers to progressively increase a primary frequency of a phasenumber greater than one (1) to a desired higher frequency.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there are shown in thedrawings forms which are presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIGURE 1 is a schematic illustration of saturating cores connected to anine phase source.

FIGURE 2 is a schematic illustration of tripler connection which may beconnected to a nine phase source.

FIGURE 3 is a shcematic illustration of a circuit for providing ninephase currents from a three phase source.

FIGURE 4 is a vector diagram illustrating the relative phase andvoltages for the circuit of FIGURE 3.

FIGURE 5 is a schematic illustration of a modification of the circuitshown in FIGURE 3.

FIGURE 6 is a schematic illustration of a circuit diagram for convertingthree phase 60 cycle current to single phase 540 cycle current forapplication to an induction furnace.

Referring now to the drawings in detail, wherein like numerals indicatelike elements, there shown in FIGURE '1 a composite diagram of ninewound saturating cores 10 connected to a nine phase supply. The ninephase supply has phase progression in the order 1, 2, 3, 4, 5, 6, 7, 8and 9 as indicated in the drawing. The cores 10 are connected to threeneutral points brought out as I, II and III. Neutral point I, which mayalternatively be referred to as output terminal I, is associated withthe wound cores 10 that are connected to phases 1, 4 and 7. Neutralpoint II is associated with the cores 10 that are connected to phasepoints 2, 5 and 8. Neutral point III is associated with the cores 10that are connected to phase points 3, 6 and 9. The cores 10 connected tophase points 1, 4 and 7 and to neutral point I constitute a firsttripler group. Cores 10 connected to phase points 2, 5 and 8 and neutralpoint II comprise a second tripler group, and cores 10 connected tophase points 3, 6 and 9 neutral point III comprise a third triplergroup.

The cores 10 in each of the tripler groups may be provided with a commonsecondary winding which is connected with similar secondary windings inthe other two groups to provide a three phase power supply, This isshown in FIGURE 2. The series connected secondary windings 12 12 12 7 1414 14 and 16 16 16 associated with each of the first, second and thirdtripler groups are interconnected by the conductor 18 and brought out atpoints I, II and III to form a three phase triple frequency powersupply. It should be noted that each of the cores in each of the first,second and third tripler groups is Y connected at neutral points 20, 22and 24.

Under saturating conditions from a nine phase source, the secondaryneutral points I, II and II in FIGURE 2 are output terminals for a threephase current at three times input frequency. However, if points I, IIand III are to be used, not only must a means be provided for supplyingsubstantially nine phase power to input points 2 9, but also a circuitfor closing the path of the 3()) currents back through points I, II andIII must be provided.

FIGURE 3 illustrates a circuit which provides a nine phase current froma three phase source while at the same time providing circuitry forcompleting the three phase, 3( current path established at points I, IIand III. As shown, the circuit includes six coils connected to form anirregular hexagon. The coils 26, 28, 30, 32, 34 and 36 areinterconnected at points designated F, D, N, L, K, and G. The woundcores 10 are tapped otI coils 26 6 at points 1, 2, 3, 4, 5, 6, 7, 8 and9. Cores 10 are connected at their opposite ends in the manner shown inFIG- URE 1, with neutral points I, II and III being brought out asshown. Winding 2636 provide a circuit to fulfill the requirements of anine phase source and closed circuit path.

FIGURE 4 is a mixed vector diagram which illustrates the relative phasesand voltages for the circuit connection of FIGURE 3. In FIGURE 4 acircle 38 with its center at Y is drawn through points 1, 2 9representing the relative phase relations of cores 10. Radials 1-Y, 2-Y,3Y, 4-Y, 5-Y, 6Y, 7-Y, S-Y, and 9Y are drawn so that the included anglebetween pairs of radials is 40 electrical degrees. This establishes thenine phase re lationship with a phase progression of 1, 2 9 as set forthin the description of FIGURE 1. A second set of vector lines of equallength to represent equal intensities, is drawn through points 23, 56,and 89. A vector line N-D parallel to the line 2-3 is drawn throughpoint 7. A vector line K-L parallel to vector 8-9 is drawn through point4. And a vector line GF parallel to line 5-6 is drawn through point 1.By thusly drawing the vector lines, an irregular hexagon with parallelopposite sides is completed. Moreover, a circle with nine radialsintersecting the irregular hexagon has been developed such that theradials are equally spaced at 40 electrical degrees.

By comparing FIGURES 3 and 4 it is apparent that vector line L-N inFIGURE 4 represents windings L-N in FIGURE 3 and vector line FG, whichis parallel, represents winding F-G. This indicates that thecorresponding windings are magnetically tightly coupled such as wouldoccur when they are wound on the same core. The same analysis alsoapplies when parallel vectors F-D and KL are compared to windings F-Dand K-L, and also when parallel vectors KG and ND are compared withwindings K-G and N-D.

Trigonometric analysis of the irregular hexagon shown in FIGURE 4 showsthat vector line F-G is 82.9 percent of the length of vector line LN.This relative vector length can be used to measure turn ratios. Thus,the relationship between vectors F-G and L-N can be used to indicatethat the turn ratio of winding F-G to LN is .829. Stated otherwise, thisindicates a ratio of 1.00 to 1.20 for each pair of parallel windings. Asimilar analysis applies to the relationship between the remainingvectors and windings. Thus, if the vector diagram shown in FIG- URE 4 isaccurately drawn the turn ratio or tapping points of the otherconnection points such as 2, 3, etc., may be established using ameasuring scale. Trigonometric methods may also be used to establish theturn ratios or voltage ratios to any degree of accuracy. Analysis alsoindicates that vector lines KG, FD, and LN are intercepted by radials ata distance from their ends of approximately 22 percent of their length.

Table I gives some of the more useful relations which can be derivedfrom the vector diagram of FIGURE 4.

Table I .V0ltage or turn ratios between designated points Points: RatioH-Y .543 GY .647 1-G .293

L-S .156 5-6 .395 F-L 1.2922 AF .293

Since phase points A(1), B(4), and C(7) are midpoints of similarwindings and together define an equilateral triangle represented by thedotted line in FIGURE 4, they may be used as an input connection pointsfor a three phase power source. The nine phase terminals are establishedat points 1, 2, 3, 4, 5, 6, 7, 8 and 9. The respective trianglesestablished by points 1, 4 and 7; 2, 5 and 8; and 3, 6 and 9 arecongruent representing the three coil assemblies having outputs at I, IIand III in FIGURE 3.

The mid-points M, E and H of the windings 32(LN), 28(FD), 36(KG)opposite to windings GF, KL and DN having mid-points A, B and C may alsobe chosen for connection to a three phase source. In this case the ninephase voltages are about 6.4 percent higher than the voltages producedby connections to points A, B and C. Thus, in either case, the windingmid-points may be used for three phase source connections where thesource voltage is suitable for saturating the cores of windings 10.

Where the source voltage is not suitable for saturating the cores ofwindings 10, another set of coupled windings connected in Y or A can beused to obtain the desired nine phase points. By way of example, a deltaconnected primary winding is shown in FIGURE 5. The primary windings 40,42 and 44 arranged in delta connection and adapted for connection to athree phase source A, B and C. Windings 40, 42 and 44 are magneticallycoupled to coils 26, 30' and 34. Otherwise, FIGURE 5 represents aschematic connection for producing the nine phase voltage which is thesame as that of FIGURE 3.

As indicated above, the vector diagram of FIGURE 4 shows that parallelsides of the hexagon configuration are magnetically coupled.Accordingly, parallel windings shown in FIGURES 3 and 5 are magneticallyclosely coupled. This is achieved by winding parallel windings on thesame transformer core. Accordingly, a standard three leg three phasecore may be used. That is, primary winding 40 is inductively coupledwith windings GF and LN on the same transformer core. Similarly winding44 is inductively coupled with windings LK and DF on the sametransformer core, and winding 42 is inductively coupled on the sametransformer core with windings ND and GK.

Referring now to FIGURE 6, there is shown a schematic diagram of astatic frequency multiplier for increas ing a three phase source atcommercial frequencies to a single phase frequency at nine times thesource of frequency. The output current is applied to an inductionfurnace 60. As shown, the static frequency multiplier in FIGURE 6 uses atransposer for developing a nine phase frequency source in the manner ofthe circuit shown in FIGURE 3. Thus, although the windings have beenpositioned differently to better illustrate the device, theirconnections are the same and they are magnetically coupled on the samecores described with respect to the FIGURE 3.

The saturable cores (1), 10(2) 10(9) are connected to a nine phasesource represented by winding 26-36. In FIGURE 6 the saturable cores ofwindings 10 are grouped in their respective tripler group representingphases 1, 4 and 7; 5, 8 and 2; and *6, 9 and 3. As with the connectionshown in FIGURE 3, their output is taken from points I, II and III.Three saturable cores and windings 46, 48 and 50 are connected to outputpoints I, II and III. A neutral connection at the other end of cores 46,48 and 50 is provided at 52. As thus connected windings 46, 48 and 50form a fourth tripler group. Secondary windings 54, 56 and 58 aremagnetically coupled to the saturable cores 46, 48 and 50. Windings 54,56 and 58 are arranged in open delta connection. An induction heatingfurnace is represented by coil 60 is connected between the openterminals of secondary windings 54, 56 and 58. A capacitor 62 isconnected between output I and III. A second capacitor 64 is connectedbetween output points I and II. A third capacitor 66 is connectedbetween output points H and III.

The capacitors 62, 64 and 66 will absorb certain portions of theharmonic components of current that may be generated, but the thirdharmonic and odd multiples thereof are not absorbed by these capacitors.Thus, capacitors 62, 64 and 66 act as shunting capacitors for allharmonics except the third harmonic and odd multiples thereof.

Capacitors 68 and 70 together with saturable reactor 72 are connected inparallel with the induction heating coil 60 to provide power factorcorrection. As shown, capacitor 70 may be switched into and out of thecircuit by means of switch 74 to adjust the power factor. Similarly,means may be provided to adjust the inductive capacity of saturable corereactor 72 to provide further fine tuning.

As thus described, the circuit shown in FIGURE 6 transposes three phasesource to a nine phase current by means of a transformer connection inthe form of an irregular hexagon. The three phases are tapped olf at thepoints 1, 2, 3 9 and connected to 3 tripler groups of three saturatingcores and winding 10. The 3 tripler groups, consisting of phases 1, 4and 7, phases 5, 8 and 2, and phases 6, 9 and 3 respectively, aresymmetrical and act as triplers to produce an output current at 3 timesthe input frequency. The 3(f) output current is taken from neutralpoints I, II and III and connected to a fourth tripler represented bythe primary coils 46, 48 and 50 and the secondary coils 54, 56 and 58.The secondary coils 54, 56 and 58 are connected in open delta to a load60. The frequency applied to load '60 is nine times the input frequency.

The nature of the connections described above, permits the three phase3( currents at points I, II and III to divide into three generally equalcomponents. That is, in the tripler represented by phases 1, 4 and 7 andthe neutral point I, equal 3( currents flow back from point I throughsaturating elements 10 10., and 10 into appropriate tapping points onthe hexagonally connected transposer. These currents flow through thetransposer windings such that the algebraic sum of the 3(f) currents toand from the hexagonal transposer is zero in conformity with standardthree phase alternating current analysis.

By means of a diagram such as that shown in FIG- URE 4, with theirregular hexagon representing the 6 tapped and interconnected windingsof the transposer and the radials representing the saturating elements,it has been determined that there is an ampere-turn dissymmetry to the3(f) current in the transposer. A delta connected winding on the 3 coresof the transposer will effectively cancel the unbalanced ampere-turnwith minor power loss and highly satisfactory current balance. Thegeneral value of the compensating ampere-turns is approximately by theformula:

i n =.l2i n where: i represents the compensating current n representsthe number of compensating turns i; represents the tripler current nrepresents the number of turns on the transposer windings correspondingto 26, 30 and 34 in FIGURE 3.

The compensating winding is represented in FIGURE 6 by the coils 76, 78and 80 connected in delta formation. Being thusly connected, thecompensating winding may also serve the double purpose of being both acompensating winding and the primary source winding. This is shown inFIGURE 5. If the winding 76, 78 and 80 of FIGURE 6 is used for thisdouble purpose, the conductors size is adjusted to carry the powercurrent and the compensating current. Star connected primaries (notshown) could also be used.

It has been found advantageous to insert linear chokes 82, 84 and 86between the appropriate capacitors 62, 64 and 66 and the neutralconnections I, II and III for the tripler assemblies of FIGURE 6. Thefunction of chokes 82, 84 and 86 may be taken over by auxiliary cores inthe tripler elements which are magnetically parallel to the saturatingcores. Such auxiliary cores have low but relatively stable permeabilityat high magnetizing forces, as is described in co-pending applicationSer. No. 216,503, filed Aug. 13, 1962, and entitled Frequency Tripler.The chokes 82, 84 and 86, or their functional equivalent help tostabilize the operation of equipment by adjusting the apparent magneticsaturation characteristic of tripler elements 46, 48 and 50, so that the3(f) voltage across terminals I, II and III does not need impracticallyclose adjustment.

The saturating elements 46, 48 and 50 are preferably made ofmagnetically oriented steel laminations wound into toroidal form toproduce a sharp knee in the magnetizing curve. The slope of themagnetizing curve beyond the knee is raised enough to allow a practicalrelationship between the applied 3 (f) voltage and the triplermagnetizing current in the high saturation region. The saturatingelement 10 may also have auxiliary stabilizing cores to improve theirperformance and stability in relation to source voltage.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specification as indicating the scope of theinvention.

I claim:

1. A static frequency multiplier comprising a phase multiplyingtransformer for increasing the phase number of a multi-phase source, andcascaded frequency multipliers electrically connected to the increasedoutput phases of said transformer, said frequency multipliers beingconnected to increase the frequency of the source by a number equal tothe increased output phase number of said transformer.

2. A transposer for increasing the phase number of a multi-phase sourcecomprising a transformer core having three legs, a pair of windings oneach leg, one winding on each leg having a greater number of turns thanthe other winding by a predetermined ratio, all said windings beingelectrically connected with each winding in a pair being separated by ahigh and low turn ratio winding of the remaining pairs, and tappingpoints on each winding, said tapping points being at equally spacedelectrical phase angles.

3. A transposer for increasing the phase number of a multi-phase sourcecomprising a transformer core having three legs, first and secondwindings on each leg, said first and second windings being in a ratio ofapproximately 1.00 to 1.20, a center tap on each of said first windings,a pair of taps on each of said second windings at a predetermined numberof turns from the ends thereof, said windings being electricallyconnected in a series so that each winding in a pair is separated by afirst and second winding of the remaining winding.

4. A transposer in accordance with claim 3 wherein said taps on saidsecond windings are spaced approximately 22% of the turns from the endsthereof.

5. A static frequency multiplier comprising a phase multiplyingtransformer for converting a three phase alternating current input to anine phase output, said nine phases being spaced apart by an equalnumber of electrical degrees, first, second and third frequency triplerunits, said first unit being associated with a first, fourth and seventhtransformer output phase, said second unit being associated with asecond, fifth and eighth transformer output phase, said third unit beingassociated with a third, sixth and ninth transformer output phase, saidtripler units being connected to develop a three phase output at threetimes the input frequency of said transformer.

6. A static frequency multiplier in accordance with claim 5 including afourth tripler unit electrically connected to the triple frequencyoutput of said first, second and third tripler units, said fourthtripler unit developing a single phase output at nine times the inputfrequency of said transformer.

7. A static frequency multiplier comprising a transformer for increasingthe phase number of a multi-phase source comprising a transformer corehaving three legs, a pair of windings on each leg, one winding on eachleg having a greater number of turns than the other winding by apredetermined ratio, said windings being electrically connected so thateach winding in a pair is separated by a high and low turn ratio windingof the remaining pairs, a center tap on said windings having a lessernumber of turns, a pair of taps spaced inwardly by a predetermined equalnumber of turns from opposite ends of said windings having a greaternumber of turns, first, second and third tripler units electricallyconnected to said taps for developing a three phase output at threetimes the input frequency of said static frequency multiplier.

8. A static frequency multiplier in accordance with claim 7 including afourth tripler unit electrically connected with the three phase triplerfrequency output of said first, second and tripler units for developingan output at nine times the input frequency of said static frequencymultiplier.

9. A static frequency multiplier in accordance with claim 7 wherein saidpairs of windings have a turn ratio of approximately 1.00 to 1.20, andsaid windings having a larger number of turns are tapped atapproximately 22% of the turns from their ends.

10. A static frequency multiplier comprising a transformer forconverting a three phase input into a nine pha-se output, saidtransformer including a transformer core having three legs, first andsecond windings on each leg, said first and second windings having aturn ratio of approximately 1.00 to 1.20, a center tap on said firstwindings, a pair of taps on said second winding each spaced inwardly apredetermined number of turns from opposite thereof, each set of firstand second windings being electrically connected so that each winding isseparated by a first and second winding of the remaining windings,first, second and third frequency tripler units connected to said ninephase transformer output, said first, second and third tripler unitsconnected for developing a three phase output at three times the inputfrequency of said frequency multiplier, and a compensating windingmagnetically coupled with each of said first windings to neutralizeharmonic frequency current unbalance created by said first, second andthird tripler units.

11. A static frequency multiplier in accordance with claim 10 whereinthe ampere-turns of said compensating winding is related to that of saidfirst winding in accordance with the following:

i nb=.12ifll i represents the compensating current n represents thenumber of compensating turns i; represents tripler unit current 11represents the number of turns on the first transposer windings.

12. A static frequency multiplier in accordance with claim 10 whereinsaid first windings on each leg are secondary windings magneticallycoupled to primary windings wound on said legs, the current carryingcapacity of said primary windings adapted to cancel said currentincluded in said primary windings, said primary windings beng connectedin delta.

13. A static frequency multiplier comprising a phase multiplyingtransformer for increasing the phase number of a 3-phase source to 9,three frequency triplers connected to the increased output phases ofsaid transformer to provide a 3-phase frequency at three times thesource frequency, said frequency triplers being connected to provide areturn circuit for the increased frequency developed by said triplers.

14. A static frequency multiplier in accordance with claim 13 wherein afourth frequency tripler is connected to the output of said threefrequency triplers for producing a single phase output at nine times thesource frequency.

15. A static frequency multiplier in accordance with claim 13 whereinthe nine phases are equally spaced at angles of forty electricaldegrees, and each of said three frequency triplers has a neutral point,said frequency triplers being connected to develop a voltage at theneutral point which is three times the source frequency.

16. A static frequency multiplier in accordance with claim 15 wherein afourth frequency tripler is connected to the neutral points of saidthree frequency triplers, said fourth frequency tripler being atransformer having a primary and secondary, said primary being connectedin Y to the output of said three frequency triplers, and the secondaryof said frequency tripler being connected in open delta to provide avoltage at nine times the frequency of the source.

17. A transposer for increasing the phase number of a multi-phase sourcecomprising three sets of first and second windings, one winding in eachset having a greater number of turns than the other winding by apredetermined ratio, the windings in each set being closely magneticallycoupled, all of said windings being electrically connected to each otherwith each winding in a set being separated by a high and low turn ratioWinding of the remaining sets, and tapping points on each Winding.

18. A transposer in accordance with claim 17 wherein the turns ratiobetween the windings in each set is approximately 1.00 to 1.20, a centertap on each of the windings having a lower number of turns, two spacedapart taps on each of the windings having a greater number of turns,each of said two taps being spaced inwardly by an amount equal toapproximately 22% of the turns from the ends of said windings having agreater number of turns.

19. A static frequency multiplier comprising a transformer forincreasing the phase number of a multi-phase source, said transformerincluding three sets of first and second windings, one winding in eachset having a greater number of turns than the other winding by apredetermined ratio, the windings in each set being closely magneticallycoupled, all of said windings being electrically connected to each otherwith each winding in a set being separated by a high and low turn ratiowinding of the remaining sets, and tapping points on each winding, theturns ratio between the windings in each set being approximately l.0O to1.20, a center tap on each of the windings having a lower number ofturns, two spaced apart taps on each of the windings having a greaternum ber of turns, each of said two taps being spaced inwardly by anamount equal to approximately 22% of the turns from the ends of saidwindings having a greater number of turns, said transformer beingconnected to produce a nine phase output from a three-phase input, threesets of frequency triplers connected to provide a three-phase output atthree times the source frequency of said transformer, and, a fourthfrequency tripler connected to the output of said three sets offrequency triplers for producing a single phase output at nine times thesource frequency.

20. A transposer in accordance with claim 17 including a compensatingwinding for neutralizing ampereturn dissymmetry when said transposer isconne tced to a frequency multiplier.

21. A transposer in accordance with claim 20 wherein said compensatingwinding is connected in delta, said compensating winding being coupledto said sets of windings and being wound to be connected as atransformer primary winding for said transposer.

22. A static frequency multiplier comprising a phase multiplyingtransformer for increasing the phase number of a multiphase source toprovide an increased number of symmetrically spaced phases, frequencymultiplier means electrically connected to the increased output phasesof said transformer, said frequency multiplier means being electricallyconnected to points on the transformer windings to provide asymmetrical, balanced multi-phase output of increased frequency relativeto the frequency of said multi-phase source.

References Cited UNITED STATES PATENTS 3,309,604 3/ 1967 B-ussey 321-683,311,810 3/1967 Sample 321-68 1,948,119 2/1934 Lobl 321-7 2,470,598 5/1949 Biebesheimer 336-12 2,790,131 4/ 1957 Nyyssonen 321-57 3,026,467 3/1962 Barnes 321-5 3,219,834 11/1965 Smithies 321-57 X FOREIGN PATENTS116,701 3/1959 U.S.S.R.

JOHN F. COUCH, Primary Examiner.

WARREN E. RAY, Examiner.

G. GOLDBERG, Assistant Examiner.

